Oscillators are used in a range of applications from reference clocks and frequency references, to distance measurements (e.g., RADAR) and radio technologies. An oscillator is a device that provides an AC output signal at a given frequency in response to an input DC power. Once powered, a self-sustained oscillator continues to oscillate until the power is removed. A resonating system with a positive feedback is typically used to make a self-sustained oscillator. A resonating stage with a positive feedback creates a non linear system which maintains oscillations at a given frequency (wω0) and given amplitude (Aosc).
FIG. 1 shows a block diagram of an exemplary prior art self-sustained oscillator. The thermal motion of the resonator is amplified and its phase is corrected to provide a feedback signal that drives the resonator. When the gain of the amplifier is sufficiently large to compensate for the intrinsic damping of the resonator and for losses due to the transduction technique (e.g., electrical to mechanical and mechanical to electrical), the system starts to self-oscillate. Typically, the only input an oscillator uses is DC power in order to bias the one or more internal amplifiers that provide the feedback gain. Finally, the motion of the resonator can be converted to an electrical signal by a transducer. The electrical signal can then be used for frequency sources, clocks, or other applications.
A resonator exhibiting a large quality factor (Q) can provide a more stable oscillator. With their large Q, mechanical resonators, such as those made from quartz crystals, micro electro-mechanical systems (MEMS), or nano electro-mechanical systems (NEMS) are particularly well suited for use in oscillators.
There is a need for more stable, more efficient, and lower noise oscillators.